The previous paper of our series explored the effects of the stellar bulk
motion on the formation of Wolf-Rayet stars. Indeed, the fastest runaway
massive stars of the Milky Way are strong-winded and bow-shock-free Wolf-Rayet stars
carrying circular rings, which challenged our understanding of the formation of
Wolf-Rayet nebulae [1]}.
A typical example is the nebula M1-67 around the star WR124 [2]}.
The proposed simple solution for their formation scenario teaches us that the
stellar motion of the driving star does not influence the growth
of Wolf-Rayet nebulae, since the region of free-streaming between stellar surface
and main-sequence wind bubble's termination shock is sufficiently extended. This
is largely the case for high-latitude objects, as the diluted medium therein favors
the production of huge and extended bow shocks, making room for wind-wind shell
collision to happen without being affected by the ISM material.
Importantly, the absence of observed ISM material in Wolf-Rayet
nebulae [3]}, [4]} indicates that
most Wolf-Rayet shells, including bipolar Wolf-Rayet nebulae, are probably
produced this way, and, this further implies that the large-scale wind-blown bubble
can be ignored when numerically modelling them.
